Deep well pump



Nvfzi, 1939.

w. l.. CONNOR 2,180,864

DEEP WELL PUMP Filed Oct. 14, 19,35 2 Sheets-Sheet l -Nov. 2l, 1939.

W. L. CONNOR DEEP WELL PUMP Patented Nov. Z1, 1939 ,Ururiaov STATI-:s

PATENT OFFICE DEEP WELL PUlVIP Application October 14, 1935, Serial No. 44,818

8 Claims.

My invention relates to reciprocating pumps, and is directed toa pump construction especially applicable to deep well installation.

The principal object of my invention is to pro- `51 vide a pump that Will deliver an exceptionally large quantity of fluid for a given length of stroke.

The engineer attacking the problem of adequate pumping fromv the exceedingly deep wells that are becoming more numerous in current oil 10'l production,is confronted by at least four important limiting considerations. `These considerations should be given some thought for a proper understanding of the present invention.

First, there is the fact that the cross-sectional l1'5 area of an oil pump must be confined to the dimensions -of the discharge tubing, which, in

turn, must be accommodated by the Well casing. Of necessity, therefore, the pump itself may be no larger than two or three inches in diametel.

Secondly, the usual power equipment installed at a Well provides for a limited length of pump stroke, partly from custom and standards established in pumping Wells of moderate depth, and partly because of the rgreater investment and high operating cost involved in using equipment for longer pump strokes. The power required to liftthe long column of oil in a deep well taxes standard equipment; to increase the amplitude of the pump stroke without reducing the number of strokes per minute may further so tax prevailing power equipment as to ybe impractical, or, at best, to involve serious offsetting losses. For example, it must be borne in mind that increasing the throw of a pump crank increases the acceleration and velocity of the long oil column and string of' rods.r

The third important consideration is that because of theinordinate weightof the oil column in a deep well, and because of the excessive distance separating the power unit from the pump, resiliency of the string of rods becomes a serious loss factor. This stretch in the pump rods is subtracted from the power stroke at the surface to net the effective stroke at the pump.

Finally, increasing the number of strokes per minute has serious disadvantages. In current practice, it is common, because of the stretch in vthe rods Yat a great depth, to use a relatively small pump at a compensatingr relatively high number of strokes per minute. Two cost factors enter here. In the rst place, the more rapidly a pump operates for a given rate of production, the more Wear and the higher the ratio of cost of pump l replacement to production. In the second place,

the greaterthe number of times the string of rods must be stretched for a given quantity of production, the greater the waste of power.

The advantagesl ofmy invention may be readily understood in the light of the four consid- 5 erationsv recited. By providing for increased volume of oil flow per unit length of pump stroke, within the restricted cross-sectional area of Well tubing, I compensate for motion lost in the stretch of the rods, and do so withoutengender- 10 ing diiculties inherent .either in increasing the length of the strokes,v or in increasing the rate of the strokes Standard power equipment may be utilized at customary speeds, and pump replacement Will be normalfor any-given well. 15

vI accomplish increased pump capacity by incorporating two pumping units in tandem in a single pump structure, arranging for one of the pumping units to pump into or through the other pumping unit. I `Broadly described, my invention comprises two pump cylinders in telescopic relation adapted for relative movement longitudinally, each cylinder carrying a piston that is effective with the other cylinder, a fluid passage being provided 25I to permit one cylinder to pump either into or through the other cylinder.

Thev recital of other objects, advantages and features of my-'invention is, for the purpose of better understanding, reserved for the detailed 30 description to follow. In this disclosure, the principles of my. invention are, for illustration, embodied in a removable typepump.

' In the accompanying drawings:

Fig. l is a broken elevation, largely in section, 3-5.

of my pump installed in a Well tubing;

Figs. 2, 3, and 4, taken together, comprise an enlarged axial section similar to Fig. l; Fig. 5 is a horizontal section taken on line 5-5 of Fig. 3;

Fig. 6 is a horizontal section taken on line 6-6 of Fig. 3; u Fig. '7 is a `fragmentary axial section indicating a modied construction whereinA one of the pump valves is omitted; and 4.5.,

Fig. 8 is a fragmentary axial section indicating how my invention may be modied by adding 'a bottom discharge valve.

Pump'jacket I0 is incorporated in the usual discharge tubing through which oil is pumped to 50 the surface of the well. Threaded to the bottomv of the jacket, as an extension thereof, is standing valve shoe Il, which has the usual tapered seat I2 and inwardly disposed annular shoulder i3. From the vbottom of the standing 55 valve shoe, a gas anchor plug III and further tubing (not shown) may extend if required.

Under normal pumping conditions, an expansion mandrel l5 is removably seated in standing valve shoe Il. Shoulders l5 on flexible extensions il o1 the mandrel engage the aforementioned annular shouder I3 of the standing valve shoe.

Expansion mandrel i5 supports the stationary parts of my pump, including a lower standing valve generally designated I9, a lower and outer cylinder I9, and a tube or small cylinder 29; while the movable parts of the pump, including an inner and upper cylinder 2l, are supported and moved by sucker rod 22.

It will be noted that mandrel l5, together with standing valve shoe II, forms a seal between, on the one hand, the well-pressure zone below the pump and outside the pump jacket, andon the other hand, the tubing-pressure Zone within the jacket that is subject to the tremendous weight of the oil column extending to the top of the well.

Standing valve cage 23 is in the form of a coupling in threaded engagement with expansion mandrel I5, and, in the usual manner, is provided with ball guides 23a. Suitably secured between cooperating surfaces of the expansion mandrel and the valve cage is a valve seat 2A to receive ball 25. The range of the lball upward is limited by a suitable diametric stop 26, the stop being integral with a nipple 21 threaded into the upper end of valve cage 23. 'Ihe upper portion of nipple 2'! is reduced in diameter and threaded to receive a spider generally designated by numeral 28, and is further reduced at its upper extremity 27a and cut away to provide a plurality of radially disposed ports 29,

Spider 28 comprises a lower tubular portion 3!) threaded on its inner and outer peripheral surfaces. a plurality of integral legs 3|, and an integral, upper, restricted ring-portion 32. The outer threads of the spider provide convenient means for mounting lower and outer cylinder I9 to expansion mandrel I5. l

Tube 2li is provided at the bottom with an integral annular shoulder 33 and is dimensioned to lit through ring 32 with shoulder 33 engaging the ring from below. with the weight of the tube on the upper end of nipple 21. A liberal clearance is provided between the lperiphery of the tube and ring 32 and also between annular shoulder 33 and the legs 3l of the spider. By virtue of this arrangement, the-tube is secured against longitudinal movement but has a substantial degree of lateral freedom.

It will be apparent that' the interior of tube 2t is in communication with passage 34 leading upward from standing valve I8 and also, by virtue of ports 29 and the spaces between the legs of the spider, is in communication with an annular pump chamber 35 between the tube and outer cylinder I9.

ll/lounted to the top of tube 20 by threaded engagement is a relatively extensive, annular piston 3b (Fig. 2) dimensioned to cooperate with travelling inner cylinder 2l for pumping action. In the preferred form of my invention, this Piston serves as an extension lof tube 2li and is provided with an upper standing valve generally designated by numeral 3l.` In the drawings, valve cage 38, threaded to piston 36 as an extension thereof, is provided with the usual ball .guides 99 and stop pin 4D, and cooperates with the upper end of the piston to secure a valve seat il for receiving ball 42.

Threaded to the lower end of sucker rod 22 is valve cage i3 oi an upper travelling valve that is generally designated by numeral 44. The valve cage is provided with ports 45 communicating with the tubing-pressure Zone exterior of the pump. Secured between cooperating surfaces of the valve cage and a 4nipple 46 that is threaded to the cage, is a valve seat 4l to receive ball 43. Nipple 45 in turn supports, by threaded engagement, the aforementioned inner cylinder 2l.

Mounted to the lower end of inner cylinder 2| by threaded engagement is a relatively, extensive, annular, travelling piston 49 dimensioned to cooperate both with tube 25 and with outer cylinder i9 for pumping action. 'Ihe purpose of kthe lateral freedom of the bottom of the tube will now be apparent: by virtue of the clearance provided, the tube will automatically adjustitself to any inaccuracy in the boring and machining oi the travelling piston.

Annular space 59, defined by tube 20, travelling cylinder 2i, and the two pistons, expands and contracts with the action of the pump. It is essential that this space be vented to the tubing-pressure zone exterior of the pump, For this purpose, the wall of travelling cylinder 2l may be provided with suitable vent ports 5| near the top edge of travelling piston 49, and around the above these ports the outer surface 0f the inner travelling cylinder map be either cut longitudinally or reduced in diameter for a surhcient longidudinal distance to extend above the top edge of standing cylinder I9, thereby providing a clearance space 52 open at all times between the inner travelling cylinder and vthe outer standing cylinder.

It is contemplated that in a typical pump, each of the two pistons will be approximately three feet long, and that the pump will be dimensioned for approximately a six-foot stroke.

The drawings indicate the disposition of the various parts of the pump at or near the bottom of the stroke. As sucker rod 22 lifts inner travelling cylinder 2i on the upward stroke of the pump, travelling valve 44 will close under pressure from the oil column in the well tubing. As travelling valve Il retreats from stationary piston llt, pump chamber 53 in the travelling Icylinder will expand; and as travelling piston 49 simultaneously retreats from the bottom end of standing cylinder i9, annular pump chamber 35 will likewise expand. On this movement, pressure from the well will open lower standing valve i3, and oil from below the pump under well pressure will iiow into upper pump chamber 53 through tube 29, opening valve 31, and oil likewise will flow through ports 29 and between legs 3l of the spider into lower annular pump chamber 35.

On this upward movement of the pump, annular space 5l) will contract, the oil therefrom escaping freely into the tubing-pressure vZone by virtue ci ports 5l and clearance space 52.

is travelling piston G9 approaches stationary piston the stationary piston cuts off ports 5I, thereby restricting flow from annular space 50 to produce a cushioning eiect at the top of the stroke.

On the downward stroke, standing valve I8 will close; oil from annular pump chamber 35 will be expelled between the legs of the spider through ports 29 and up tube 29 past valve 3l into yupper pump chamber 53; and oil from chamber 53, forcing open travelling valve 44, will be discharged into the well tubing.

On this downward stroke, annular space 50, expanding in volume, will receive oil freely from the tubing-pressure zone. My pump may be regarded as consisting of two inter-connecting pumping units: the upper pumping unit, represented by chamber 53, comprises travelling cylinder 2|, travelling valve 44, and stationary piston 36; the lower pumping unit, represented by annular chamber 35, comprises standing cylinder I S, the exterior of tube 20, travelling piston 49, and lower standing valve I8..l e

' It will be noted that it is possible for me, in effect, to arrange'two pumps in tandem to operate within the connes of well tubing, because, by virtue of tube 20, I provide for communication between the two pumps, so that, on the intake stroke, the upper pump may draw from the lower pump or through the lower pump, and on-the discharge stroke, lthe lower pump -will be permitted to deliver uid to the upper pump.

Regarded in one aspect, tube 20 on the intake stroke of the pump is merely an inflow passage from the well-pressurekzone, the tube being, in effect, a by-pass from' the well-pressure vZone to the upper pumping unit, the by-pass extending through the lower pump, rather than around it, forv economy of space and simplicity of construction. Oil entering the'intake port of the pump,

i. e., lower standing valver I8, may divide, in 'ef` feet, into two streams, one stream entering the lower pump andthe otherdstream continuing up tube 20 to the upper pump, inI which case, the

tube functions as a by-pass; or, on the other hand, the entire stream that ows throughthc lower standing valve may pass into the'l lower pump, so that the upper pump merely draws from the body of oil in the lower pump. Which of these two conditions exists depends upon the relative size and disposition of ports 29.

In the construction shown in Figs. 1 6, the term pump chamber 35. ,Y i

In either construction, on the downward` discharge stroke of the pump, tube 23 serves simply as a means for conveying oil from the lower pump to the upper pump, and the by-pass aspect does not appear.

Because two pumping units are provided'in tandem and connected to the samesucker rod for simultaneous operation, my pump will deliver va greater volume of fluid per unit length of stroke than any other reciprocating pump heretofore employed in deep wells. A simple plunger pump of the same inside diameter as the outer standing cylinder would deliver, in one stroke, a voln urne of oil equal to the length of the stroke times the tubing-.pressure Azone will remain substan tially stationary while the moving parts of the y pump slip through theA fluid, the fluid escaping from the pump through travelling valve 44. On the up stroke of the pump, when travelling valve 44 is closed,the pump moving upward displaces in the tubingv around the pump a volume equal to the volume of oil previously discharged from the pump on the down stroka'such displacement causing the oil column to'move towards the surface of the well. 5

In pumping to capacityiiuid that is relatively vfree of gas, upper standing valve 31 will remain opensubstantially all the time, "because, on ythe upward stroke, the upper pumping unit will be expanding to receiveoil through tube 20, and', on

, the downward stroke, the lower pumping unit will be contracting to expel oil through tube 2U in the same direction. It is apparent, then, that this intermediate valve, upper standing valve 31, may be omitted entirely.

The two pum-ping units are essentially pulsating chambers, and annular space 50 is a third or .intermediate pulsating chamber thatA discharges alternately withv the two pumping. units. This thirdpulsating chamber is, of course, not an effective pumping unitin the-sense of contributing directly tothe vcapacity ofthe pump by adding its volume to that of the two pumping units, since it merely draws fluid from the tubing-pressure zone and'then Areturns that uid. By arranging for free Vpassage of fluid to and from this annular space, I provide'con'tinuous pressure therein, direct from the exterior of the pump, to discourage any tendencyof fluid to seep by the pistons to this third pulsating chamber from either of the two pumping units. Such alternating flow between vthe third pulsating chamber and either of the two pumping units would detract from the capacity of the pump and might be sufficient to reduce the total capacity to that of a simple single-acting pump. VA virtue, then, of free communication in both'directions between annular space 50 and the exterior of the pump is that it tends to keep the pump functioning at full potential capacity.

One modication of Vmy pump consists simply in omitting this valve, as indicated by Fig. '7, in which vcorresponding parts are given corresponding numbers. In' that gure, stationary piston 36a is shown with an unimpeded passage.

While this intermediate valve may be omitted, I prefer to include it for two reasons: first, because it is believed that, where a high ratio of gas tofluid is being pumped, the valve may serve to break up the gas column within the pump and thereby facilitate compression of the gas for discharge from the pump; secondly, because by pro-` viding three valves, I have .a` pump that will continue to function when vany one of the three valves fails. If the intermediate valve fails to close, the volume delivered by the .pump will not .ordinarily`be affectedifuthe upper or travelling valve fails to close, the lower pumping unit will continue to function; if the lower standing valve fails to close, the upper pumping unit will continue to function. Y'

' A second modication of my invention, .as indicated by Fig, 8, corresponding numbers being used to indicate corresponding parts, is distinguished bythe addition to the lower pumping n unit of a bottom discharge `valve generally designated by numeral 56.

In this third form of my invention, a plain nipple 51, having valve stop 58, is'threaded into the top of standing valve cage 23. Threaded to the top of nipple 5l is a tubular section 5B. Threaded, in turn, to the top of'tubular section 5S is a nipple 5l) that has a reduced upper portion 5E 'threaded to receive spider 28 and a further reduced upper extremity Bla cut away to provide ports 52. Tube 2da, resting on nipple 5l, has, as noted previously, plug 54 and peripheral ports 55. Standing cylinder I9 is threaded to the base of spider 23. Y

Lower discharge valve 5G comprises a T shaped tube 63, spanning tubular section 5S, the horizontal portion of the tube, forming two ports Ell in theperiphery of tubular section 59. A suitable bushing 65 screwed into the bottom .of vertical portion St of the T secures in place a valve seat 6l that is adapted to receive ball 68. A suitable depending lug G9 within the T serves as a stor for ball 68.

On the upward stroke of the pump, this third form of my invention functions in thesame manner as the nrst two forms, lower discharge valve being closed. On the down stroke of the pump, however, fluid from the lower pumping unit may be discharged entirely through valve 56, each pumping unit discharging independently of the other. Obviously, in that case, oil would iiow through tube only on the up stroke of the pump., l

In the removable type of deep well pump here shown, the pump is removed by simply drawing sucker rod 22 upward beyond the usual range of. the pump 'strokeluntil travelling piston 49 engages stationary piston 3G. The force upward exerted by the sucker rod will then be transmitted to the stationary parts of the pump through tube 2G, and expansion mandrel I5 may readily be jarred out of engagement with shoulder It of standing valve shoe ll. The pump assembly may then be readily 'lifted to the surface of the Well. f

It is apparent, then, that, while it is desirable to restrict the cross-sectional area of tube 2B for the purpose of increasing the cross-sectional area of annular pump chamber to attain maximum pump capacity, the limit tov which the cross-sectional area of tube 2i) may be restricted will be determined by two considerations: the fact that the tube must `be large enough to accommodate, Without serious friction, the required now of iiuid through the tube; and the fact that the tube itself must be orV sujicient size and strength to accommodate strain incidental to disengaging the pump from the standing valve shoe and transporting the pump to the surface of the well. Because of this latter consideration, I prefer to use alloy steel for'. tube 20.

Restricting the cross-sectional area of tube 2d reduces the residual volume of the pump, i. e., the cubical content of the pump at the end of the discharge stroke.` When the residual volume of a pump is relatively large, the elciency of the pump may be seriously impaired by the presence of excessive gas in the oil; because the -worlr of the pump will be devoted largely to merely compressing the gas within the pump. It is believed that my pump has less residual volunie than any other pump of the same size' emcentageof Vgas `in a deep fwell V`would preclude economic operation of another type of pump.

For the purposes vof vcomplete disclosure and to illustrate the principles involved, I have described my invention as embodied in a deepwell pump of the removable type. .It is obvious that the inventionmay be applied to pumps of other types for other purposes. It will also be apparent that my invention may be subject to a wide range of material modication and change without departing from the principles involved. I reserve the right to all such modification and change that rcome within the scope of my appended claims. For instance-a reversed form suggested by the present disclosure is shown and described in my co-pending application, serially numbered 44,319, led on the samefdate, and likewise entitled Deep well pump.

I-Iaving described my invention, I claim:

l. A pump having in combination: an inner tube and an outer `cylinder concentrically arranged and spaced from each other to form an annular space therebetween, said tube and cylinder being joined together by a iiuid-tight connection adjacent the lower end of the outer cylinder; a non-return, valve-controlled inlet port adjacent the lower end of the outer cylinder; a constantly open port in the inner tube adjacent its lower end, above the inlet port, communicating with `said annular space; a plunger comprising a cylindrical member telescopically arranged between said inner tube and outer cylinder; a non-return, Valve-controlled discharge port in said plunger; a non-return valve controlled discharge port .adjacent the lower end of the outer cylinder intermediate the inlet port and said constantly open port in the inner tube; an annular piston on the inner tube to cooperate with the plunger for pumping action; and a second annular piston on the plunger to slidingly engage the inner tube and the outer cylinder for pumping action, said pistons isolating the annular space therebetween, which increases and decreases in volume upon reciprocation of the plunger, the plunger being provided with a constantly open port venting said otherwise isolated annular space to the exterior of the pump.

2. A pump havingv in combination: an inner tube and an outer cylinder concentrically arranged and spaced from each other to form an annular space therebetween, said tube and cylinder being `ioined together by a fluid-tight connection adjacent the lower end of the outer cylinder; a non-return, valve-controlled inlet port adjacent the lower end of the outer cylinder; a check valve associated with the inner tube to prevent downward flow therethrough; a constantly open port in the inner tube adjacent itslower end, above the inlet port, communicating with said annular space; a plunger comprising a cylindrical member telescopically arranged between said inner tube and outer cylinder; a non-return, valve-controlled discharge port in said plunger; a non-return valve controlled discharge port adjacent the lower end of the outer cylinder intermediate the inlet port and said constantly open port in the inner tube; an annular piston on theinner tube' to cooperate with the plunger for pumping action; and a second annular piston on the plunger to slidingly engage-the inner tube and the outer cylinder for pumping action, said pistons isolating the annular space therebetween, which increases and decreases in volume upon reciprocation of the plunger, the plunger being provided with aconstantly open portvent-v ingisaid otherwise isolated annular-space tothe exterior of the pump. ,l f 4 3. A pump having in combination: an inner tube and an vouter cylinder concentrically arranged andspaced from each other to forman annular space therebetween; a uid-tight wall connecting said tubeand cylinder adjacent their lowerends, sealing the lower end of the annular space;.an1inlet port through saidjwall leading to the inner tube; an upwardly opening nonreturn valve forkv said port; a constantly open portin the inner tube adjacent its lower end, above the inlet port, communicating withsaid annular'fspace; aplungercomprising a cylindrical member telescopically arranged between said inner tube and outer cylinder of slightly less outer diameter than the inner diameter of the outer cylinder; a non-return valve controlled discharge port adjacent the lower end of the outer cylinder intermediate the inlet port and said constantly open port in the inner tube; an annular piston on the inner tube adapted to cooperate with the plunger for pumping action; and a second annular piston on the vplunger to slidingly engage the inner tube and the outer cylinder for pumping action, said pistons isolating the annular space therebetween, which increases and decreases in volume upon reciprocation of the plunger, the plunger being provided with a constantly open p'ort, above its piston, venting the otherwise isolated annular space laterally through the side of the plunger to the space intermediate the plunger wall and the outer cylinder.

4. A duplex pump for wells, a tubing rin which the pump is positioned comprising a stationary barrel, a standing valve mounted in the stationary barrel adjacent the lower end thereof, a stationary piston, a conduit extending from adjacent the standing valve through the stationary piston, a traveling barrel within the stationary barrel, said traveling barrel extending over the stationary piston, a traveling piston mounted on the traveling barrel, said piston surrounding-said conduit, there being a pumping chamber above the stationary piston and in the traveling barrel, a second pumping chamber below the traveling piston and in the stationary barrel, a check valve mounted at the upper end of the traveling barrel and sucker rod connecting means on the traveling barrel, a bottom discharge valve mounted in the stationary barrel above the standing valve and below the lower pumping chamber, said bottom discharge valve opening into the tubing whereby liquid from the bottom pumping chainber is discharged through said bottom discharge valve into the tubing, and closure means between the tubing and the stationary barrel, said closure means being arranged below the bottom discharge valve.

5. A duplex pump for wells, a tubing in which the pump is positioned comprising a standing valve, a stationary. barrel mounted on the standing valve and rising therefrom, a pull tube mounted on the standing valve and rising therefrom, a traveling barrel positioned within the stationary barrel, a check valve mounted on the upper end of the traveling barrel, sucker rod coupling means on the traveling barrel, a traveling piston mounted on the traveling barrel, a stationary piston mounted on the upper end of the pull tube, said piston being positioned within the traveling barrel, the traveling piston encircling the pull tube and operating in the stationary barrel, said pump having an upper pumping chamber above: vthel stationary piston, a lower pumping chamber 1 below. the traveling piston, both offsaid .chambers simultaneously drawing the liquid .through :the standing valve and simultaneously discharging liquid through the valve on the upper.- end of the traveling barrel, and a bottom vdischarge valve in the stationary barrel andabove the standing valve, said bottom discharge valve-having ports opening into the tubing, .'saidfbottom discharge lvalve being adapted and arranged ,toy discharge the v'liquid from the lower pumping ,chamber into the tubing, and closure -means between the tubing and the stationarybarrel, said-'closurameans being arranged below the bottom discharge valve.

6. A duplex pump for wells, a tubing in which the pump is positioned comprising a standing valve, a stationary barrel mounted on the standing valve and rising therefrom, ra pull tube mounted on the standing valve and rising therefrom, a traveling barrel positioned within the stationary barrel, a check valve mounted on the upper end of the traveling barrel, sucker rod coupling means on the traveling barrel, a traveling pis-ton mounted on the traveling barrel, a stationary piston mounted on the upper end of the pull tube, said piston being positioned Within the traveling barrel, the traveling piston encircling the pull tube and operating in the stationary barrel, said pump having an upper pumping chamber above the stationary piston, a lower pumping chamber below the traveling piston, both of said chambers simultaneously drawing the liquid through the standing valve and simultaneously discharging liquid through the valve on the upper end of the traveling barrel, a `lock;- ing shoe depending from the standing valve, said locking shoe being releasably held in the tubing, a valve mounted in the stationary piston, and a bottom discharge valve in the stationary barrel and above the standing valve, said bottom discharge valve being adapted and arranged to discharge the liquid from the lower pumping chamber into the tubing, and closure means between the tubing and the stationary barrel, said closure means being arranged below the bottom discharge valve. y

7. A duplex pump for wells, a tubing in which the pump is positioned comprising a standing valve, a locking shoe depending from the standing valve, said locking shoe being releasably held in the tubing, a bottom discharge valve housing iixedly mounted on the standing valve and arranged above said standing valve, a valve in said housing, said housing having ports opening into the tubing, said valve controlling the ow from within the pump to said ports, a stationary barrel mounted on the standing valve and rising therefrom, a stationary pull tube mounted on said housing and rising therefrom, a stationary piston mounted on the upper end of the pull tube, a traveling barrel extending over the stationary piston kand arranged within the stationary barrel, a traveling piston mounted on the lower end of the traveling barrel, said traveling piston surrounding the pull tube, said pump having a lower pumping chamber below the traveling piston and within the stationary barrel, said pull tube having ports therein opening into said pumping chamber, and a check valve mounted on the upper end of the traveling barrel, and closure means between the tubing and the stationary barrel, said closure means being arranged below the bottom discharge valve.

8. A duplex pump for wells, a tubing in which thepump' is positioned comprisinga standing va1ve,a locking shoedepending from the. stand',- ing valve, said lockingshoerbeing releasably held in the tubing,` a bottom rdischarge valve housing xedly mounted on the standing valve and arranged above said standing valve, a valve in said housing., said housing having ports opening into the. tubing, said valve controlling the flow from Within the pump to said ports, a stationary barrely mounted on the standing valve and rising therefrom, .a .stationary pull tube.` mounted. on said housing and rising therefrom, a stationary piston mounted onthe upper endr of the pulltube, a travelingfbarrel extending over the stationary piston and arranged within the stationarypbar.- rel, a traveling piston mounted onthe lower end off. the travelingibarrehsaid travelingL piston surrounding Athe pull tube, said pump havinga lowernpumping chambervv below the traveling. piston` and Within thestationary.' barrel,V said. pull tube. having ports therein opening into. said pumpingchamberVa check valve mounted .on the upperfend of the traveling barre1, and a check valve mounted on the upper end. of the stationary piston, and closure Ymeans, between the tubing andA they stationary barreLwsaid, closure means beingrarrangedlbelow. the bottom discharge valve.

WILLIAM L. CONNOR. 

